1. Field of the Invention
The present invention relates to an image display system. In particular, the present invention relates to an image display system through which an image is displayed on an image-formation device such as a screen on which an image is displayed and a position of an image formed due to that a user indicates such position can be detected when the user indicates the position.
2. Description of Related Art
Recently, it is spread and progressed an image display technology to conduct explanations to many people while displaying a text formed through a PC (personal computer) on a screen by utilizing a liquid crystal projector. In a case that such explanations are done, to assist comprehension of audience, it is general that an explainer/an assistant indicates description, figures, tables and the like in the image displayed on the screen by an indicating tool such as an indicating stick or a beam pointer corresponding to explanation.
In this indication, there will be a case that it is requested to detect a position indicated by the above indicating tool. For example, there will be conceivable a case that various image processes to assist comprehension of audience are desirably done based on the above indication as a trigger, so that a color of sentence indicated by the indicating tool is changed and the sentence is displayed with highlights or a figure indicated by the indicating toll is enlarged and displayed.
As the technology to realize the above request, it is proposed in Unexamined Japanese Publication No. 2001-273092 a technology that the indicated position within an image area displayed on the screen is detected by taking the image of the image area and by conducting an edge process of the image obtained.
In the above case, it can be adopted a method to extract an outline of the indicating tool by conducting an image process of images taken from the screen and the indicating tool. However, it is requested larger machine power to conduct the image process according that the area to which the image process is conducted becomes wider. And if a large image display is done through the liquid crystal projector, it is requested a considerably large machine power, thereby there is a problem that cost thereof increases.
Further, although it is conceivable a method to detect a top position of the indicating toll by utilizing an infrared sensor, infrared ray emitted from the infrared sensor reflects on a portion other than the top portion of the indicating tool, thus it is difficult to determine whether or not the infrared ray is reflected on the top portion of the indicating tool. As a result, there will also exist a problem that it is very difficult to correctly obtain the position information of the indicating tool.